The sizes of passenger cars manufactured in the United States have decreased in the past few years. Most of the size decrease has been through a reduction in the size of the trunk. An even further size reduction is anticipated within the next decade which could essentially eliminate the trunk as a place for the transportation of luggage. Since a majority of vehicle owners have become accustomed to traveling distances requiring overnight stops, it has been suggested that small cargo trailers could offer a solution to the transportation of luggage. However, it is important that stability be maintained between the towing vehicle and the trailer, especially when travelling above 50 miles per hour.
One form of instability exhibited by tow vehicle-trailer combinations currently available has been trailer sway. Swaying causes the trailer to oscillate in a manner similar to the movement of a pendulum. This instability often causes severe yawing in the trailer which can lead to loss of steering control of the tow vehicle. With the anticipated weight reduction of future vehicles, the loss of steering control from such instability could be accelerated.
To alleviate sway instability, some trailers have been equipped with dampening devices attached to the hitch such as the shock absorbers located on opposite sides of the hitch as disclosed in U.S. Pat. No. 3,722,920, and the friction disc arrangement disclosed in U.S. Pat. No. 3,785,680. These anti-sway devices operate sufficiently as long as the tow vehicle-trailer is moving in a straight line. However, when it is desired to turn the tow vehicle-trailer combination, the tow vehicle must overcome the resistance of the anti-sway devices.
In an effort to overcome the turning resistance of anti-sway devices, a power cylinder, disclosed in U.S. Pat. 3,834,480, is operationally responsive to the fluid in a power steering system for allowing the trailer to track the tow vehicle during turning operations.
In all the known prior art devices, the stability of the tow vehicle-trailer combination is dependent on the ability of the tow vehicle to dampen the instability. Unfortunately, with the anticipated reduction in weight of future passenger cars such stability will be reduced.